These types of air mass sensor record the air mass flow which flows into a collector. The collector communicates via induction tubes with cylinders of the internal combustion engine and supplies these with fresh air.
Ever more stringent legal requirements relating to pollutant emissions in motor vehicles make it necessary to set the air/fuel mixture in the individual cylinders of the internal combustion engine very precisely. This requires that the air mass drawn into the relevant cylinder is determined very precisely. The air mass sensor allows the air mass flowing into the collector to be determined very precisely. By means of corresponding physical models of the collector and the induction tubes and of the induction behavior of the cylinders of the internal combustion engine, the air mass flowing into the cylinders of the internal combustion engine can be determined very precisely.
Known air mass measurers are regularly embodied in the form of a Whetstone bridge, with a high-resistance temperature-dependent resistor to compensate for the temperature of the induction air in one branch and a low-resistance temperature in the other branch of which the heat performance is characteristic for the air mass flowing past. The heating resistor is generally embodied as a so-called hot-film resistor. During the operation of the internal combustion engine particles of dirt and also oil droplets build up on the hot-film resistor. The result is that the behavior of the measuring resistor changes.